High requirements for reliability are placed on line systems, which guide liquid media, since these are often central components of safety-related devices. In such cases, the operational reliability of line systems as a component of cooling apparatuses has to be constantly checked since a failure of the line system, due for example to leaks or clogging, can cause high levels of damage.
If, for example, the line system guides liquid media such as water, one known method for monitoring a line system of this kind consists in continuous sensing of the current flow of the liquid medium in the line system as a parameter. A so-called water-pressure function is used to determine a so-called theoretical pressure of the liquid medium from the sensed parameters. The theoretical pressure of the liquid medium is the pressure obtained by inserting the current flow of the liquid medium from the water-pressure function. After measuring the current pressure of the liquid medium in the line system, the difference between the current pressure of the liquid medium and the theoretical pressure of the liquid medium is determined. The resulting differences are, for example, used as a measure for the clogging or as a measure for the size of the leak in the line system and is constantly compared against a prespecified tolerance. If the tolerance is exceeded for a lengthy period, an alarm is issued as an indication of a fault in the line system.
Here it is a drawback that the sensed parameters are generally exposed to a high level of noise which triggers unnecessary false alarms. In order to avoid this, relatively high tolerances are specified, wherein this in turn has a negative impact on reliability. A further drawback consists in the fact that the difference determined between the current pressure of the liquid medium and the theoretical pressure of the liquid medium only identifies a tendency for the measure for the clogging. Therefore, it is generally difficult to specify sensible values for the tolerances with which both few false alarms are issued and a certain degree of reliability of the monitoring is provided.
Known from DE 10 2009 051 931 A1 is a method for early leak detection in a cooling device for cooling an engineering plant. With this method, two controllable values are arranged in a line at a certain distance one behind the other. Two pressure sensors are arranged between the two valves. Each of the two pressure sensors is arranged in the vicinity of one of the two valves. The actual pressures are sensed and compared with expected pressures. The comparison is used to draw conclusions regarding the presence of a leak.
It is known from AT 513 042 B1 to repeatedly sense a pressure difference and an actual flow in a line system and to determine therefrom the hydraulic resistance of the line system. The hydraulic resistance determined is output in a visual form. It is also possible to check automatically whether the hydraulic resistance determined lies within a permitted range. If the hydraulic resistance is out of the range, a warning signal may be output.
It is known from JP H01 149 109 A to shut off a section of a line system on the output side by means of a valve, then to expose it to pressure and finally to shut it off on the input side as well by means of a further valve. The pressure in the section of the line system is then sensed and evaluated.
It is known from AT 513 042 B1 to determine a drop in pressure and a flow rate at a particular time and to calculate the hydraulic resistance therefrom. On the basis of this variable it is then decided whether residues or leakages are present. The hydraulic resistance can be displayed on a monitor. A permitted range for the hydraulic resistance can be defined. A warning message is output when the hydraulic resistance is out of the permitted range. In AT 513 042 B1 a formula for calculating the hydraulic resistance is specified, which can be considered the flow function.